Thin film transistor and display

ABSTRACT

A thin film transistor capable of reliably preventing the entry of light into an active layer, and a display including the thin film transistor are provided. A thin film transistor includes: a gate electrode; an active layer; and a gate insulating film arranged between the gate electrode and the active layer, the gate insulating film including a first insulating film, a first light-absorbing layer and a second insulating film, the first insulating film arranged in contact with the gate electrode, the first light-absorbing layer arranged in contact with the first insulating film and made of a material absorbing light of 420 nm or less, the second insulating film arranged between the first light-absorbing layer and the active layer.

CROSS REFERENCES TO RELATED APPLICATIONS

The present invention contains subject matter related to Japanese PatentApplication JP 2008-063915 filed in the Japanese Patent Office on Mar.13, 2008, the entire contents of which being incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a thin film transistor (TFT) includingan active layer made of an oxide conductor or silicon (Si), and adisplay including the thin film transistor.

2. Description of the Related Art

Thin film transistors have been widely applied as fundamental technologyfor liquid crystal displays or organic EL (Electro Luminescence)displays. As a typical semiconductor film which is an active layer forthe displays, a silicon (Si) film in a noncrystalline state (a so-calledamorphous silicon film) or a polysilicon film crystallized by an excimerlaser or solid-phase growth is used. Moreover, in recent years, it hasbeen proposed that as a semiconductor film, a metal oxide capable ofbeing formed by a low-cost apparatus such as a sputtering method isused.

In most of thin film transistors using a silicon film for an activelayer, a light-shielding film is arranged to prevent light from enteringthe silicon film. Moreover, it has been known that in a metal oxidesemiconductor, a change in electrical conductance occurs due tophotoinduction (for example, refer to Japanese Unexamined PatentApplication Publication No. 2007-115902 (FIG. 8)), so it has beenproposed to arrange a light-shielding film.

SUMMARY OF THE INVENTION

However, as a material of a light-shielding film, a material havingelectrical conductivity such as a metal or silicon is used, so in termsof influence on characteristics of a thin film transistor, it isdifficult to bring a light-shielding film and an active layersufficiently close to each other, and light may not be sufficientlyshielded. Moreover, manufacturing steps are complicated by arranging thelight-shielding film.

It is desirable to provide a thin film transistor capable of reliablypreventing the entry of light into an active layer, and a displayincluding the thin film transistor.

According to an embodiment of the invention, there is provided a thinfilm transistor including the following components (A) to (C):

(A) a gate electrode;

(B) an active layer; and

(C) a gate insulating film arranged between the gate electrode and theactive layer, the gate insulating film including a first insulatingfilm, a first light-absorbing layer and a second insulating film, thefirst insulating film arranged in contact with the gate electrode, thefirst light-absorbing layer arranged in contact with the firstinsulating film and made of a material absorbing light of 420 nm orless, the second insulating film arranged between the firstlight-absorbing layer and the active layer.

According to an embodiment of the invention, there is provided a displayincluding: a thin film transistor and a display device on a substrate,in which the thin film transistor is composed of the thin filmtransistor according to the above-described embodiment of the invention.

In the thin film transistor according to the embodiment of theinvention, the gate insulating film includes the first insulating filmarranged in contact with the gate electrode, and the firstlight-absorbing layer arranged in contact with the first insulating filmand made of the material absorbing light of 420 nm or less and thesecond insulating film arranged between the first light-absorbing layerand the active layer, so a distance between the first light-absorbinglayer and the active layer becomes extremely small, and the entry oflight into the active layer is reliably prevented, and characteristicsare stabilized. Therefore, in the display including the thin filmtransistor, for example, in a liquid crystal display, leakage of anelectric charge in a liquid crystal storing period is prevented, anddegradation in display quality such as contrast or luminance isprevented.

In the thin film transistor according to the embodiment of theinvention, the gate insulating film includes the first insulating filmarranged in contact with the gate electrode, the first light-absorbinglayer arranged in contact with the first insulating film and made of thematerial absorbing light of 420 nm or less and the second insulatingfilm arranged between the first light-absorbing layer and the activelayer, so the distance between the first light-absorbing layer and theactive layer is able to become extremely small, and the entry of lightinto the active layer is able to be reliably prevented.

In the display according to the embodiment of the invention, the thinfilm transistor with stabilized characteristics according to theembodiment of the invention is included, so high display quality is ableto be achieved.

Other and further objects, features and advantages of the invention willappear more fully from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of the whole configuration of a liquid crystaldisplay including a liquid crystal display panel according to a firstembodiment of the invention.

FIG. 2 is a sectional view of a configuration of a part of the liquidcrystal display panel illustrated in FIG. 1.

FIG. 3 is a sectional view of a configuration of a TFT illustrated inFIG. 2.

FIG. 4 is an illustration for describing changes in characteristics ofthe TFT by light.

FIG. 5 is an illustration for describing the thickness of alight-absorbing layer.

FIG. 6 is an illustration for describing a distance between a firstlight-absorbing layer and an active layer.

FIGS. 7A, 7B and 7C are sectional views illustrating a method ofmanufacturing the TFT illustrated in FIG. 3 in order of steps.

FIGS. 8A and 8B are sectional views illustrating steps following FIGS.7A, 7B and 7C.

FIG. 9 illustrates changes in characteristics in the case where light isapplied and in the case where light is not applied.

FIG. 10 is a sectional view of a configuration of a TFT according to asecond embodiment of the invention.

FIG. 11 is a sectional view of a modification of the TFT illustrated inFIG. 10.

FIG. 12 is an illustration of a configuration of a display according toa third embodiment of the invention.

FIG. 13 is an equivalent circuit diagram of an example of a pixel drivecircuit illustrated in FIG. 12.

FIG. 14 is a sectional view of a configuration of a display regionillustrated in FIG. 12.

FIG. 15 is a plan view of a schematic configuration of a moduleincluding the display according to the foregoing respective embodiments.

FIG. 16 is an external perspective view of an application example 1 ofthe display according to the foregoing respective embodiments.

FIGS. 17A and 17B are an external perspective view from the front sideof an application example 2 and an external perspective view from theback side of the application example 1, respectively.

FIG. 18 is an external perspective view of an application example 3.

FIG. 19 is an external perspective view of an application example 4.

FIGS. 20A to 20G illustrate an application example 5, FIGS. 20A and 20Bare a front view and a side view in a state in which the applicationexample 5 is opened, respectively, and FIGS. 20C, 20D, 20E, 20F and 20Gare a front view, a left side view, a right side view, a top view and abottom view in a state in which the application example 5 is closed,respectively.

FIG. 21 is a sectional view of a modification of the TFT illustrated inFIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments will be described in detail below referring to theaccompanying drawings.

First Embodiment

FIG. 1 illustrates the configuration of a liquid crystal displayaccording to a first embodiment of the invention. The liquid crystaldisplay is used for a liquid crystal television or the like, and theliquid crystal display includes, for example, a liquid crystal displaypanel 1, a backlight section 2, an image processing section 3, a framememory 4, a gate driver 5, a data driver 6, a timing control section 7and a backlight driving section 8.

The liquid crystal display panel 1 displays a picture on the basis of apicture signal Di transmitted from the data driver 6 in response to adriving signal supplied from the gate driver 5. The liquid crystaldisplay panel 1 includes a plurality of pixels PI arranged in a matrixform, and is an active matrix liquid crystal display panel in which eachpixel P1 is driven individually. Each pixel P1 is composed of, forexample, a liquid crystal display device, and displays any one of basiccolors, that is, red (R), green (G) and blue (B).

The backlight section 2 is a light source applying light to the liquidcrystal display panel 1, and includes, for example, a CCFL (Cold CathodeFluorescent Lamp), an LED (Light Emitting Diode) or the like.

The image processing section 3 performs predetermined image processingon a picture signal S1 from outside through the use of a storage section3A to produce a picture signal S2 which is an RGB signal.

The frame memory 4 stores the picture signal S2 supplied from the imageprocessing section 3 for each pixel P in a frame.

The timing control section 7 controls the timing of driving the gatedriver 5, the data driver 6 and the backlight driving section 8.Moreover, the backlight driving section 8 controls the illuminationoperation of the backlight section 2 according to the timing control ofthe timing control section 7.

FIG. 2 illustrates a sectional configuration of the liquid crystaldisplay panel 1. The liquid crystal display panel 1 includes a liquidcrystal layer 30 between a TFT substrate (a drive substrate) 10 and afacing substrate 20. Polarizing plates 41 and 42 are arranged on the TFTsubstrate 10 and the facing substrate 20, respectively, so that opticalaxes (not illustrated) of the polarizing plates 41 and 42 are orthogonalto each other.

In the TFT substrate 10, a TFT 12 and a pixel electrode 13 made of ITO(Indium Tin Oxide) or the like are formed in each pixel P1 on a glasssubstrate 11. An interlayer insulating film 14 is arranged between theTFT 12 and the pixel electrode 13. The pixel electrode 13 iselectrically connected to the TFT 12 via a connection hole 14A arrangedin the interlayer insulating film 14. In the glass substrate 11, acapacitive element (not illustrated) or the like is arranged.

The facing substrate 20 is formed by forming a common electrode 22 madeof ITO on a glass substrate 21. On the glass substrate 21, a colorfilter and a black matrix or the like (not illustrated) are formed.

FIG. 3 illustrates an example of the TFT 12. The TFT 12 is formed, forexample, by laminating a gate electrode 51, a gate insulating film 52,an active layer 53, a stopper layer 54, a source electrode 55S and adrain electrode 55D, an interlayer insulating film 56, and source wiring57S and drain wiring 57D in order on the glass substrate 11.

The gate electrode 51 has a thickness of, for example, 65 nm, and ismade of molybdenum (Mo). The active layer 53 has a thickness of, forexample, 50 nm, and is made of an oxide semiconductor such as an IGZO(InGaZnO)-based, InZnO-based, ZnO-based, SbSnO-based, SrTiO₃-based orTiO₂-based oxide semiconductor.

The gate insulating film 52 is arranged between the gate electrode 51and the active layer 53, and includes a first insulating film 52A madeof silicon nitride (SiN), a first light-absorbing layer 52B, and asecond insulating film 53B made of silicon dioxide (SiO₂) in order fromthe gate electrode 51. The first light-absorbing layer 52B is made of amaterial absorbing light of 420 nm or less. Thereby, in the TFT 12, theentry of light into the active layer 53 is able to be reliablyprevented.

FIG. 4 illustrates results obtained by examining changes incharacteristics of a TFT including an active layer made of IGZO bychanging the wavelength of light applied to the TFT. It is obvious fromFIG. 4 that when light of 420 nm or less, particularly light of 350 nmor less is applied, a threshold voltage is largely shifted to the left,and the state of the TFT is the same as the state in which the TFT isconstantly on. In Japanese Unexamined Patent Application Publication No.2007-115902, it is described that a change in the electrical conductanceof an oxide semiconductor occurs by photoinduction; however, only anincrease in off current is expected from the change. A large shift ofthe threshold voltage as illustrated in FIG. 4 was first discovered bythe inventors of this invention.

More specifically, the first light-absorbing layer 52B is preferablymade of amorphous silicon. It is because unlike a metal film, the firstlight-absorbing layer 52B does not need perfect light shieldingproperties, and it is only necessary for the first light-absorbing layer52B to prevent the entry of light of 420 nm or less into the activelayer 53. Moreover, there is an advantage that the first insulating film52A, the first light-absorbing layer 52B and the second insulating film52C are able to be formed successively, so it is not necessary toincrease the number of manufacturing steps.

The thickness of the first light-absorbing layer 52B is preferablywithin a range from 10 nm to 100 nm both inclusive. It is obvious fromFIG. 5 that in a wavelength range of 420 nm or less, a sufficiently highabsorption coefficient is obtained when the thickness of the firstlight-absorbing layer 52B is within the range, for example,approximately 50 nm.

FIG. 6 is an illustration for describing a positional relationshipbetween the first light-absorbing layer 52B and the active layer 53. Adistance D between the first light-absorbing layer 52B and the activelayer 53 is preferably equal to a distance L between an end (a point A)of the active layer 53 and an end (a point B) of the firstlight-absorbing layer 52B (D=L). In other words, light entering from thebacklight section 2 into the active layer 53 the most easily is light nenter from a side into the active layer 53. The light n enters at 45° inan interface between air and the glass substrate 11. A perpendicularline is drawn from the end (the point A) of the active layer 53 to thefirst light-absorbing layer 52B to form a triangle ABC. To shield thelight n, in the triangle ABC, tan θ=D/L, that is, tan 45°=D/L=1, therebyD=L is derived. When the first light-absorbing layer 52B is formed inthe gate insulating film 52, the distance L is able to be reduced. Onthe other hand, for example, in the case where a light-shielding film isarranged, for example, on a back surface of the glass substrate 11, thedistance D is increased, thereby it is necessary to increase thedistance L accordingly, so an aperture ratio may be reduced. On theother hand, when the distance L is reduced, the light n entering fromthe side may not be able to be absorbed by the first light-absorbinglayer 52B.

The stopper layer 54 illustrated in FIG. 3 has a thickness of, forexample, 20 nm, and is made of silicon dioxide (SiO₂). The sourceelectrode 55S and the drain electrode 55D each have a thickness of, forexample, 65 nm, and are made of molybdenum (Mo). The interlayerinsulating film 56 is made of, for example, silicon nitride(SiN)/silicon dioxide (SiO₂). The source wiring 57S and the drain wiring57D each are made of, for example, titanium (Ti)/aluminum (Al)/titanium(Ti), and are connected to the source electrode 55S and the drainelectrode 55D, respectively, through the interlayer insulating film 56.

The liquid crystal display is able to be manufactured by, for example.the following manufacturing method.

At first, as illustrated in FIG. 7A, the gate electrode 51 made of theabove-described material with the above-described thickness is formed onthe glass substrate 11 by, for example, sputtering.

Next, as illustrated in FIG. 7B, the first insulating film 52A, thefirst light-absorbing layer 52B and the second insulating film 52C whichare made of the above-described materials with the above-describedthicknesses are successively formed on the gate electrode 51 by, forexample, PECVD (Plasma Enhanced Chemical Vapor Deposition). Morespecifically, the first insulating film 52A made of silicon nitride(SiN) is formed. Next, the first light-absorbing layer 52B made ofamorphous silicon is formed by stopping supplying material gases exceptof silane, and flowing only silane. After that, the supply of thematerial gases except for silane is initiated to form the secondinsulating film 53B made of silicon dioxide (SiO₂). Thereby, withoutincreasing the number of manufacturing steps and without the need forchanging conditions, the gate insulating film 52 including the firstinsulating film 52A, the first light-absorbing layer 52B and the secondinsulating film 52C is able to be formed by simple steps. Moreover,unlike the case where a light-shielding film is arranged on the backside of the glass substrate 11, there is little possibility that thefront side of the glass substrate 11 is soiled, and cleaning is notnecessary, and it is extremely suitable for mass production.

Next, as illustrated in FIG. 7C, the active layer 53 made of theabove-described material with the above-described thickness is formedby, for example, sputtering. After that, as illustrated in FIG. 8A, thestopper layer 54 made of the above-described material is formed abovethe gate electrode 51, and as illustrated in FIG. 8B, the sourceelectrode 55S and the drain electrode 55D made of the above-describedmaterial are formed.

After the source electrode 55S and the drain electrode 55D are formed,the interlayer insulating film 56 made of the above-described materialis formed, and through holes are formed in the interlayer insulatingfilm 56, and then the source wiring 57S and the drain wiring 57D made ofthe above-described material are formed. Thereby, the TFT 12 illustratedin FIG. 3 is formed.

When the TFT was actually formed by the manufacturing method, and lightas backlight was applied from the back surface of the obtained TFT, asillustrated in FIG. 9, compared to the case where the light was notapplied, a change in characteristics was not observed. In other words,it was confirmed that when the first light-absorbing layer was arranged,the entry of light into the active layer was prevented, andcharacteristics were able to be stabilized.

After the TFT 12 is formed, the interlayer insulating film 14 is formed,and a connection hole is arranged by patterning. Next, the pixelelectrode 13 is formed, and patterning is performed so as to form apredetermined shape. Thereby, the drive substrate 10 is formed.

Moreover, the common electrode 22 is formed on the glass substrate 21 bya normal manufacturing method so as to form the facing substrate 20.

After the drive substrate 10 and the facing substrate 20 are formed,they are arranged to face each other, and a sealing layer (notillustrated) is formed around them, and a liquid crystal is injectedinto the inside of the sealing layer to form the liquid crystal layer30. Thereby, the liquid crystal display panel 1 illustrated in FIGS. 2and 3 is formed. The liquid crystal display panel 1 is incorporated in asystem including the backlight section 2, the image processing section3, the frame memory 4, the gate driver 5, the data driver 6, the timingcontrol section 7 and the backlight driving section 8 so as to completethe liquid crystal display according to the embodiment.

In the liquid crystal display panel 1, as illustrated in FIG. 1, theimage processing section 3 performs image processing on the picturesignal S1 supplied from outside so as to produce the picture signal S2for each pixel P1. The picture signal S2 is stored in the frame memory4, and the picture signal S2 is supplied to the data driver 6 as thepicture signal S3. On the basis of the picture signal S3 supplied insuch a manner, line-sequential display driving operation is performed ineach pixel P1 by a driving voltage outputted from the gate driver 5 andthe data driver 6 to each pixel P1. Thereby, illumination light from thebacklight section 2 is modulated by the liquid crystal display panel 1to be outputted as display light.

In this case, the gate insulating film 52 includes the first insulatingfilm 52A, the first light-absorbing layer 52B made of the materialabsorbing light of 420 nm or less, and the second insulating film 52C,so the distance D between the first light-absorbing layer 52B and theactive layer 53 becomes extremely small, and the entry of light into theactive layer 53 is reliably prevented, and the characteristics arestabilized. Therefore, leakage of an electric charge in a liquid crystalstoring period is prevented, and degradation in display quality such ascontrast or luminance is prevented.

Thus, in the embodiment, the gate insulating film 52 of the TFT 12includes the first insulating film 52A, the first light-absorbing layer52B made of the material absorbing light of 420 nm or less, and thesecond insulating film 52C, so the distance D between the firstlight-absorbing layer 52B and the active layer 53 is able to becomeextremely small, and the entry of light into the active layer 53 is ableto be reliably prevented. Therefore, when a display using the TFT 12 isconfigured, high display quality is able to be achieved, because thecharacteristics of the TFT 12 are stabilized.

Second Embodiment

FIG. 10 illustrates the configuration of a TFT according to a secondembodiment of the invention. The TFT has the same configuration as thatof the TFT 12 described in the first embodiment, except that a secondlight-absorbing layer 58 is arranged on the interlayer insulating film56.

The second light-absorbing layer 58 prevents light from above fromentering the active layer 53. The material and the thickness of thesecond light-absorbing layer 58 are the same as those of the firstlight-absorbing layer 52B. Moreover, as illustrated in FIG. 11, thesecond light-absorbing layer 58 may be arranged between two interlayerinsulating films 56A and 56B.

Third Embodiment

FIG. 12 illustrates an example of a configuration in which the foregoingrespective embodiments of the invention are applied to an organiclight-emitting display (an organic EL display). A third embodiment isthe same as the first embodiment, except that a display device iscomposed of an organic light-emitting device, and the functions andeffects of the third embodiment are the same as those in the firstembodiment. Therefore, like component are denoted by like numerals.

The display is used as a ultra-thin organic light-emitting color displayor the like, and in the display, a display region 110 where a pluralityof organic light-emitting devices 60R, 60G and 60B which will bedescribed later as display devices are arranged in a matrix form on, forexample, a TFT substrate 61 is formed, and a data driver 6 and a gatedriver 5 as drivers for picture display are formed around the displayregion 110.

A pixel drive circuit 140 is formed in the display region 110. FIG. 13illustrates an example of the pixel drive circuit 140. The pixel drivecircuit 140 is formed in a layer lower than a first electrode 71 whichwill be described later, and the pixel drive circuit 140 is an activedrive circuit including a driving transistor Tr1 and a writingtransistor Tr2, a capacitor (retention capacitor) Cs between the drivingtransistor Tr1 an the writing transistor Tr2, an organic light-emittingdevice 10R (or 10G or 10B) connected to the driving transistor Tr1 inseries between a first power source line (Vcc) and a second power sourceline (GND). The driving transistor Tr1 and the writing transistor Tr2each are composed of the TFT 12 described in the first embodiment or thesecond embodiment. In particular, in the TFT 12 illustrated in FIG. 10or FIG. 11 in the second embodiment, the second light-absorbing layer 58is able to prevent light emitted from the organic light-emitting devices60R, 60G and 60B from entering the active layer 53 from above.

In the pixel drive circuit 140, a plurality of signal lines 120A arearranged in a column direction, and a plurality of scanning lines 130Aare arranged in a row direction. An intersection between each signalline 120A and each scanning line 130A corresponds to one (a subpixel) ofthe organic light-emitting devices 60R, 60G and 60B. Each signal line120A is connected to the data driver 6, and an image signal is suppliedfrom the data driver 6 to a source electrode of the writing transistorTr2 through the signal line 120A. Each scanning line 130A is connectedto the gate driver 5, and a scanning signal is sequentially suppliedfrom the gate driver 5 to a gate electrode of the writing transistor Tr2through the scanning line 130A.

FIG. 14 illustrates a sectional view of the display region 110. In thedisplay region 110, the organic light-emitting device 60R emitting redlight, the organic light-emitting device 60G emitting green light andthe organic light-emitting device 60B emitting blue light are formed inorder in a matrix form as a whole. The organic light-emitting devices60R, 60G and 60B each have a planar strip shape, and a combination ofadjacent organic light-emitting devices 60R, 60G and 60B constitutes onepixel.

The organic light-emitting devices 60R, 60G and 60B each have aconfiguration in which the first electrode 71 as an anode, aninterelectrode insulating film 72, an organic layer 73 including alight-emitting layer which will be described later, and the secondelectrode 74 as a cathode are laminated in this order on the TFTsubstrate 61.

If necessary, such organic light-emitting devices 60R, 60G and 60B arecovered with a protective film 75 made of silicon nitride (SiN), siliconoxide (SiO) or the like, and a sealing substrate 81 made of glass or thelike is thoroughly bonded to the protective film 65 with an adhesivelayer 80 made of a thermosetting resin, an ultraviolet curable resin orthe like in between so as to seal the organic light-emitting devices60R, 60G and 60B. If necessary, a color filter 82 and a light-shieldingfilm (not illustrated) as a black matrix may be arranged on the sealingsubstrate 81.

The first electrode 71 is formed corresponding to each of the organiclight-emitting devices 60R, 60G and 60B. Moreover, the first electrode71 has a function as a reflective electrode reflecting light emittedfrom the light-emitting layer, and it is desirable that the firstelectrode 71 have as high reflectivity as possible so as to improvelight emission efficiency. The first electrode 71 has, for example, athickness of 100 nm to 1000 nm both inclusive, and is made of a simplesubstrate or an alloy of a metal element such as silver (Ag), aluminum(Al), chromium (Cr), titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni),molybdenum (Mo), copper (Cu), tantalum (Ta), tungsten (W), platinum (Pt)or gold (Au).

The interelectrode insulating film 72 is provided to secure insulationbetween the first electrode 71 and the second electrode 74 and toaccurately have a desired shape of a light emission region, and is madeof, for example, an organic material such as polyimide or an inorganicinsulating material such as silicon oxide (SiO₂). The interelectrodeinsulating film 72 has an aperture section corresponding to the lightemission region of the first electrode 71. The organic layer 73 and thesecond electrode 74 may be successively arranged on not only the lightemission region but also the interelectrode insulating film 72; however,light is emitted only from the aperture section of the interelectrodeinsulating film 72.

The organic layer 73 has, for example, a configuration in which a holeinjection layer, a hole transport layer, a light-emitting layer and anelectron transport layer (all of which are not illustrated) arelaminated in order from the first electrode 71 side; however, any ofthese layers except for the light-emitting layer may be arranged ifnecessary. Moreover, the organic layer 73 may have a differentconfiguration depending on the color of light emitted from the organiclight-emitting devices 60R, 60G or 60B. The hole injection layer isprovided to enhance hole injection efficiency, and is a buffer layer forpreventing leakage. The hole transport layer is provided to enhance thehole transport efficiency to the light-emitting layer. Thelight-emitting layer emits light by the recombination of electrons andholes in response to the application of an electric field. The electrontransport layer is provided to enhance electron transport efficiency tothe light-emitting layer. The material of the organic layer 73 may be atypical low-polymer or high-polymer organic material, and is notspecifically limited.

The second electrode 74 has, for example, a thickness of 5 nm to 50 nmboth inclusive, and is made of a simple substrate or an alloy of a metalelement such as aluminum (Al), magnesium (Mg), calcium (Ca) or sodium(Na). Among them, the second electrode 74 is preferably made of an alloyof magnesium and silver (an MgAg alloy) or an alloy of aluminum (Al) andlithium (Li) (an AlLi alloy). Moreover, the second electrode 74 may bemade of ITO (indium-tin complex oxide) or IZO (indium-zinc complexoxide).

The display is able to be manufactured by the following steps, forexample.

At first, as in the case of the first embodiment, the TFT 12 is formedon the glass substrate, and the pixel drive circuit 140 is formed by anormal manufacturing method to form the TFT substrate 61.

After the TFT substrate 61 is formed, the first electrode 71 made of theabove-described material is formed by, for example, DC sputtering, andthe first electrode 71 is selectively etched through the use of, forexample, a lithography technique to be patterned into a predeterminedshape. Next, the interelectrode insulating film 72 made of theabove-described material with the above-described thickness is formedby, for example, a CVD method, and the aperture section is formedthrough the use of, for example, a lithography technique. After that,the organic layer 73 and the second electrode 74 which are made of theabove-described materials are formed in order by, for example, anevaporation method, and the organic light-emitting devices 10R, 10G and10B are formed. Next, the organic light-emitting devices 10R, 10G and10B are covered with the protective film 75 made of the above-describedmaterial.

After that, the adhesive layer 80 is formed on the protective film 75.After that, the color filter 82 is arranged, and the sealing substrate81 made of the above-described material is prepared, and the TFTsubstrate 61 and the sealing substrate 81 are bonded together with theadhesive layer 80 in between. Thereby, the display illustrated in FIGS.12 to 14 is completed.

In the display, a scanning signal is supplied from the gate driver 5 toeach pixel through the gate electrode of the writing transistor Tr2, andan image signal is stored from the data driver 6 into the retentioncapacitor Cs through the writing transistor Tr2. In other words, theon-off operation of the driving transistor Tr1 is controlled in responseto the signal stored in the retention capacitor Cs, thereby a drivecurrent Id is injected into each of the organic light-emitting devices60R, 60G and 60B to cause recombination of holes and electrons, and thenlight is emitted. The light passes through the second electrode 74, theprotective film 75 and the sealing substrate 81 to be extracted. In thiscase, as in the case of the first embodiment, the gate insulating film52 includes the first insulating film 52A, the first light-absorbinglayer 52B made of the material absorbing light of 420 nm or less, andthe second insulating film 52C, so the distance D between the firstlight-absorbing layer 52B and the active layer 53 becomes extremelysmall, and the entry of light into the active layer 53 is reliablyprevented, and characteristics are stabilized. Therefore, the operationof the TFT 12 is stabilized, and the display quality is improved.

Thus, in the embodiment, as in the case of the first embodiment, thegate insulating film 52 of the TFT 12 includes the first insulating film52A, the first light-absorbing layer 52B made of the material absorbinglight of 420 nm or less and the second insulating film 52C, so thedistance D between the first light-absorbing layer 52B and the activelayer 53 is able to become extremely small, and the entry of light intothe active layer 53 is able to be reliably prevented. Therefore, whenthe display is configured using the TFT 12, the characteristics of theTFT 12 are stable, and high display quality is able to be achieved.

MODULE AND APPLICATION EXAMPLES

Application examples of the display described in the foregoingrespective embodiments will be described below. The display according tothe foregoing respective embodiments is applicable to displays ofelectronic devices displaying a picture signal inputted from outside ora picture signal produced inside as an image or a picture in any fields,such as televisions, digital cameras, notebook personal computers,portable terminal devices such as cellular phones, and video cameras.

Module

The display according to the foregoing respective embodiments isincorporated into various electronic devices such as first to fifthapplication examples which will be described later as a module asillustrated in FIG. 15. In the module, for example, a region 210 exposedfrom the sealing substrate 81 and the adhesive layer 80 is arranged on aside of the substrate 11, and an external connection terminal (notillustrated) is formed in the exposed region 210 by extending the wiringof the data driver 6 and the wiring of the gate driver 5. In theexternal connection terminal, a flexible printed circuit (FPC) 220 forsignal input/output may be arranged.

Application Example 1

FIG. 16 illustrates an appearance of a television to which the displayaccording to the foregoing respective embodiments is applied. Thetelevision has, for example, a picture display screen section 300including a front panel 310 and a filter glass 320. The picture displayscreen section 300 is composed of the display according to the foregoingrespective embodiments.

Application Example 2

FIGS. 17A and 17B illustrate appearance s of a digital camera to whichthe display according to the foregoing respective embodiments isapplied. The digital camera has, for example, a light-emitting sectionfor a flash 410, a display section 420, a menu switch 430, and a shutterbutton 440. The display section 420 is composed of the display accordingto the foregoing respective embodiments.

Application Example 3

FIG. 18 illustrates an appearance of a notebook personal computer towhich the display according to the foregoing respective embodiments isapplied. The notebook personal computer has, for example, a main body510, a keyboard 520 for operation of inputting characters and the like,a display section 530 for displaying an image. The display section 530is composed of the display according to the foregoing respectiveembodiments.

Application Example 4

FIG. 19 illustrates an appearance of a video camera to which the displayaccording to the foregoing respective embodiments is applied. The videocamera has, for example, a main body 610, a lens for shooting an object620 arranged on a front surface of the main body 610, a shootingstart/stop switch 630, and a display section 640. The display section640 is composed of the display according to the foregoing respectiveembodiments.

Application Example 5

FIGS. 20A to 20G illustrate appearances of a cellular phone to which thedisplay according to the foregoing respective embodiments is applied.The cellular phone is formed by connecting, for example, a top-sideenclosure 710 and a bottom-side enclosure 720 to each other by aconnection section (hinge section) 730. The cellular phone has a display740, a sub-display 750, a picture light 760, and a camera 770. Thedisplay 740 or the sub-display 750 is composed of the display accordingto the foregoing respective embodiments.

Although the present invention is described referring to theembodiments, the invention is not limited to the above-describedembodiments, and may be variously modified. For example, the materialand thickness of each layer, the method and conditions of forming eachlayer are not limited to those described in the above-describedembodiments, and each layer may be made of any other material with anyother thickness by any other method under any other conditions. Forexample, the first light-absorbing layer 52B and the secondlight-absorbing layer 58 may be made of silicon carbide (SiC) inaddition to amorphous silicon. Also in this case, the first insulatingfilm 52A, the first light-absorbing layer 52B and the second insulatingfilm 52C of the gate insulating film 52 are able to be formedsuccessively.

In addition, in the above-described embodiments, the configuration ofthe pixel P1 of the liquid crystal display and the configurations of theorganic light-emitting devices 60R, 60B and 60G are specificallydescribed; however, all layers are not necessarily included, or anyother layer may be further included.

Further, the present invention is applicable to a TFT with a top gateconfiguration as illustrated in FIG. 21. In this case, a silicon nitride(SiN) layer 59A and a silicon dioxide (SiO₂) layer 59B are formed on theglass substrate 11, and the active layer 53, the gate insulating film 52and the gate electrode 51 are laminated in order thereon, and arecovered with the interlayer insulating films 56A and 56B. Further, thesource wiring 57S and the drain wiring 57D are connected to the activelayer 53.

In addition, the present invention is applicable to the case where theactive layer is made of silicon.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. A thin film transistor comprising: a gateelectrode; an active layer; a source electrode and a drain electrode onthe active layer; a gate insulating film arranged between the gateelectrode and the active layer, the gate insulating film including afirst insulating film, a first light-absorbing layer and a secondinsulating film, the first insulating film being arranged in contactwith the gate electrode, the first light-absorbing layer being arrangedin contact with the first insulating film and being made of siliconcarbide, and the second insulating film being arranged between the firstlight-absorbing layer and the active layer; an interlayer insulatingfilm covering the gate electrode, the gate insulating film, the activelayer, and the source and drain electrodes, the interlayer insulatingfilm being arranged in contact with the source and drain electrodes; anda second light-absorbing layer arranged in contact with the interlayerinsulating film, the second light-absorbing layer being made of siliconcarbide.
 2. The thin film transistor according to claim 1, wherein: thefirst insulating film and the second insulating film are made of atleast one of silicon oxide and silicon nitride.
 3. The thin filmtransistor according to claim 1, wherein the active layer is made of anoxide semiconductor.
 4. The thin film transistor according to claim 2,wherein the first light-absorbing layer has a thickness of 10 nm to 100nm both inclusive.
 5. A display comprising a thin film transistor and adisplay device on a substrate, wherein the thin film transistorincludes: a gate electrode; an active layer; a source electrode and adrain electrode on the active layer; a gate insulating film arrangedbetween the gate electrode and the active layer, the gate insulatingfilm including a first insulating film, a first light-absorbing layerand a second insulating film, the first insulating film being arrangedin contact with the gate electrode, the first light-absorbing layerbeing arranged in contact with the first insulating film and being madeof silicon carbide, and the second insulating film being arrangedbetween the first light-absorbing layer and the active layer; aninterlayer insulating film covering the gate electrode, the gateinsulating film, the active layer, and the source and drain electrodes,the interlayer insulating film being arranged in contact with the sourceand drain electrodes; and a second light-absorbing layer arranged incontact with the interlayer insulating film, the second light-absorbinglayer being made of silicon carbide.